Naked Pair

Difficulty level: hard

A naked pair is two cells in the same row, column, or box whose candidates are exactly the same two numbers. Between them they must consume both numbers (one each, in some order), so no other cell in that unit can hold either value.

The power of a naked pair is not in placing a number — it is in elimination. Stripping the pair's two values from the rest of the unit often reveals naked or hidden singles that were invisible before.

The same logic extends to naked triples (three cells sharing the same three candidates) and quads, which appear in expert puzzles.

Worked example

Each highlighted cell can only hold 2 or 7 (their columns block 3 and 6). Together they claim both numbers, so 2 and 7 can be removed from the rest of row 1.
1 4 5 8 9 (highlighted) (highlighted)
3 6
6
3

How to apply it

  1. Pencil-mark candidates for the empty cells of a unit.
  2. Look for two cells whose candidate lists are identical and exactly two numbers long.
  3. Erase those two numbers from every other cell of the unit.
  4. Check whether the eliminations created new singles, and continue.

Practice it

The fastest way to internalize the naked pair is to use it. Play a free hard puzzle — the in-game hint system points out exactly this pattern when it appears, or browse the full technique library.